Question

A car is traveling at 20 meters/second and is brought to rest by applying brakes over a period of 4 seconds. What is its average acceleration over this time interval?

Answer 1

\[\color{green} {\begin{align} \vec{a} &= \dfrac{\Delta \vec{v}}{\Delta t}\\ \\&= \dfrac{\vec{v}_f - \vec{v}_i}{\Delta t} \\ \\&= \dfrac{0 - 20~\text{m/s}}{4~\text{s}}\\ \\&= -5~\text{m/s}^2 \end{align}}\]